An aromatic polycarbonate resin is used in a wide variety of fields because it has transparency and excellent flame retardancy, heat resistance and strength. However, as electronic and electric equipment parts and OA-related parts are becoming thinner, to use it in these fields, the flame retardancy of the aromatic polycarbonate resin must be further improved. High flame retardancy, for example, UL 94 V-0 rating (standards of Underwriters Laboratories of the U.S.) is often required for resins which are used in these fields. To obtain high flame retardancy, it is important that the dripping of a resin should not occur at the time of its combustion.
Polytetrafluoroethylene (may be abbreviated as PTFE) is generally known as a dripping inhibitor. However, as the secondary agglomeration of PTFE readily occurs due to the influence of static electricity, when it is mixed with an aromatic polycarbonate resin, a feed failure to the cylinder of an extruder readily occurs. Owing to its low dispersibility, it worsen the appearance of the obtained resin composition and reduces the impact strength of the composition. To improve the dispersibility of PTFE, there are proposed various methods for mixing PTFE with an organic polymer (refer to patent documents 1 to 4).
Meanwhile, molding conditions are becoming severer. For example, the injection speed is becoming faster and the molding temperature is becoming higher. Therefore, an aromatic polycarbonate resin composition which has thermal stability high enough to stand severe molding conditions is desired. That is, it is desired that an undesirable phenomenon such as the discoloration of a molded product by heat history at the time of molding does not occur under severe molding conditions. At the same time, excellent hydrolysis resistance is required for electronic and electric equipment parts and OA-related parts in order to enhance the durability of a product.
Therefore, a resin composition which improves the dispersibility in an aromatic polycarbonate resin of PTFE, is excellent in appearance, impact resistance, thermal stability and hydrolysis resistance and does not drip is desired.
Patent document 1 proposes to improve the dispersibility of PTFE by mixing it with an organic polymer. However, the obtained resin composition is not satisfactory in terms of thermal stability and hydrolysis resistance. Patent documents 2 to 4 improve the dispersibility of PTFE in the same way but it cannot be said that the obtained resin compositions are satisfactory in terms of hydrolysis resistance and also impact strength.
It is known that thermal stability is improved by adding a phosphorus-, phenol- or sulfur-based heat stabilizer to an aromatic polycarbonate resin. However, when these heat stabilizers are added, the hydrolysis resistance of the obtained resin composition greatly deteriorates.    (patent document 1) Japanese Patent No. 3,469,391    (patent document 2) JP-A 2000-297220    (patent document 3) Japanese Patent No. 3,066,012    (patent document 4) JP-A 2005-263908